no hot HVAC when stopped

[bobditts]

Hi all,

Weird issue for you. Trying to determine what the cause might be for my air to not blow hot when at a stop light. After the vehicle comes to operating temperature with the HVAC dial set to full heat and the diverter set to forward vents, it blows nice hot air while driving, but after coming to a stop, the temperature quickly drops and blows cool outside air. Any idea what I should be looking at to diagnose? I dont have any trouble lights or any indication that anything is wrong. Could it possibly be the t-stat? Thanks!

 

[Mbrooks420]

The only time I've experienced this was when there was an air bubble in the cooling system, or a low level.

 

[michael loibl]

I second that. Check the fluid in the actual Radiatior, not just the plastic tank. I’ll bet you are low, otherwise an air pocket. Worst case could be a leaking Head gasket allowing combustion gas to leak into the cooling system, But let’s hope it’s one of the first two

 

[bobditts]

Thanks for the replies. Ill top it off and purge the system.

 

[RiglerTKE]

It could also be a cracked thermostat housing. That is what happened to me later week.

 

[bobditts]

well you guys are awesome. My coolant was indeed low. Filled it up and havent had any heat/cold HVAC issues since. Curious where the coolant went. Hopefully not in the oil. Ill have to check the dipstick. Thanks!